Prolongation of intestinal allograft survival without immunosuppressive drug therapy. Transplantation of small bowel allografts.

Although survival of small-bowel allografts can be prolonged by immunosuppressive drug therapy, infectious complications have been frequent, and therefore alternate approaches have been sought. The rat model of accessory small-bowel transplantation (LBN-F leads to Lewis rat combination) was used to study the effects upon mean survival time (MST) of conveying the venous effluent from the graft through the liver (porto-portal anastomosis; PP-A) rather than into the central circulation (porto-caval anastomosis; PC-A). Also investigated was the effect of splenectomy of the host. With PC-A, the MST was 12.5 days; with PP-A, the MST was prolonged to 22.9 days (P less than 0.005); and with PC-A or PP-A and simultaneous splenectomy, the MSTs were 22 days (P less than 0.001) and 24.2 days (P less than 0.05), respectively. In the last three groups, rejection was chronic (fibrosis, partial reabsorption of the graft), rather than acute as in rats with PC-A. A rise in antidonor hemagglutinin activity paralleled the rejection process and was delayed in rats with PP-A and those with splenectomy. These results suggest that intestinal transplantation should involve PP-A rather than PC-A. Hepatic filtration or alteration of antigen originating in the graft may be the cause for delayed, chronic graft rejection. Splenectomy, acting on the efferent arm of the rejection process by decreasing the host's immune reactivity, had the same effect on the mode of graft rejection, when combined with PC-A. An enhancing effect of splenectomy, when added to PP-A, could not be elicited.